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Old 18th Oct 2020, 8:14 pm   #81
staticmind
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Default Re: B&O Capri 606 TV (17") restoration

Problem solved on the audio stage:
A tiny hairline crack in the PCB between the component 31 (20n cap, changed to 22n) caused the triode anode voltage to seem right at first, but the crack eventually progressed, causing the anode voltage to become 2.2V. The invisible crack must have occured when desoldering the old cap.

With the trace repaired, white noise is back. With the pattern generator set to generate a 1 kHz tone, I get a distorted 1 kHz tone, but as the generator is known to have an issue in the amplifier stage, the output is already of a very low amplitude. I just don't hope, that I'll need to perform a re-allignment of the IF stages, because I don't have the equipment for that. Hmm.
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Old 27th Oct 2020, 8:07 pm   #82
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Default Re: B&O Capri 606 TV (17") restoration

I have one question regarding a component on the AT1008 yoke assembly that someone might possibly help me figure out what is for. It consists of two discs/shims that can be rotated - see attached image. What is their purpose?
When removing the yoke from the defective (partially shorted heater) AW43-88, I took great care of not turning them.

Otherwise since last post I managed to:
-Heat up the the LOPT "overwind" / secondary for three days constantly dissipating 1.8W with current limited to 0.130A. The winding newer became hotter than 43-45 deg C on the surface, I'd say.

-Borrow a (partially defective) PM5509 pattern generator. The sensitivity of the TV is fine, with noise appearing in the image at 100 µV and below, see other attached image. Sound also seems fine and undistorted, but as the pots on this PM5509 need some maintenance and cleaning, it is hard to know for certain.

- Find a dry solder joint in the LOPT section. Line whistle is now completely audible and healthy, and EHT is at 13.54 kV.

- I measured the DC resistances between all the connections of the LOPT. My hope is that it makes it easier to reconstruct the LOPT, if this LOPT should ever fail. The thickness of wire would have to be determined later (when it fails).
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Old 27th Oct 2020, 8:33 pm   #83
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Default Re: B&O Capri 606 TV (17") restoration

They are picture positioning plates. They will centre the raster by rotating them moving the raster vertically and horizontally. J.
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Old 28th Oct 2020, 9:13 am   #84
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Default Re: B&O Capri 606 TV (17") restoration

Ah, thanks a lot. That makes sense.

A modification I'd also make to this Capri set is to add an NTC (VA1015) after the 120 Ohm dropper, in the heater chain. There's no reason why in particular the PY88 and PL36 in particular should light up strongly for 5 seconds when powering on the set. The previous year Capri TV 514 with the AWx3-80 had it, and so does the 1964 model Capri 610 and 1965 Capri 1965.
At least the CRT heater is at the end of the heater chain.
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Old 14th Nov 2020, 12:33 am   #85
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Default Re: B&O Capri 606 TV (17") restoration

Ok,
AW43-88 installed and chassis moved over. Opened the tuner unit as it was very dusty, and I had to unmount it in order to remove the chassis, or so I thought at least. No components were touched inside!
The AW43-88 works very well, but there is something I must have screwed up when moving the chassis over, because horizontal sync/lock is now off. The image that I have attached is supposed to show a crosshatch. It is stationary as it is, e.g image does not roll horizontally or vertically.
I have moved back to using the AW53-88 again, just to be safe.

Does anyone have any suggestions on how to debug on this, or if it is one of these common "oh, it means tube X is not in order". I assume this cannot be in the IF or tuner stages, but would be in the separator/sync phase-detector amplification stage consisting of an PCF80 and ECC82.
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Old 1st Dec 2020, 9:18 am   #86
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Default Re: B&O Capri 606 TV (17") restoration

Just to update; I actually bought a new (used) AT7635 tuner, and the problem was exactly the same. Vertical hold is fine, but horizontal hold is not, and can "pseudo-lock" into what I posted on the previous picture.

The problem was caused by the two AFC diodes in the horizontal sync. section had become open circuit. The schematic calls for two RL43, but in my original Capri 17" chassis, these were since replaced by 2x OA161. In this 21" Capri chassis, which is based on Capri 607 apparently, the AFC diodes consists of a dual package selenium diode. Picture attached. It's part number is D3-2-1Y. I am not certain as to why it decided to stop working just now, but I suspect it could be ESD, considering that it is close to the outer edge of the PCB, and it is in the Why it suddenly went O/C, I can't be certain.

I replaced with 2x OA95, and it seems to work fine.
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Old 9th Jan 2021, 11:11 pm   #87
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Default Re: B&O Capri 606 TV (17") restoration

Ok,
The TV is working fine at this point (with some fine tuning in the audio IF to be done perhaps).
I'm still working on the PSU. The original PSU section is attached to this message.

Modifications:
- Added VA1015 NTC in series with the 120 ohm dropper resistor for the heater. The 120 ohm dropper was replaced by a ~70 Ohm variable dropper resistor (USSR PEV-R 25W ceramic wirewound).
- The E250C300 selenium rectifier was replaced by a 1N4007 with a 15 ohm PEV 25W dropper resistor in series.

However, my real problem is now that the filter capacitors are rated a 320V DC max. The VA1015 NTC makes the heaters start up slowly, and therefore the B+ is present long before it is needed. As the 1N4007 is much more efficient than the selenium rectifier, and that the voltages are not 220V but 230V, I have about 325V (excluding diode drop) at the capacitors, as no current is drawn.
For now, I have a 15 ohm PEV 25W resistor in series with the fuse, in hope of dropping the voltage at the capacitors (voltage decreased due to in-rush and due the heater chain drawing more and more current).

This works, but I'm not satisfied. What if the filament in one of the tubes break, then I'll have 325V at the capacitors again?!
This is a very bare minimum power supply section, and I have no multi-tap transformer to power a dedicated circuit to detect when the heaters are on.

Isn't it considered very risky to re-implement the 60 year old selenium rectifier with a very large voltage loss over it? Does some kind of modern diode package exist with e.g. 15 1N4007 diodes in series? Some kind of small 1:1.1 transformer?

Any suggestions are very welcome.
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Old 10th Jan 2021, 6:12 am   #88
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Default Re: B&O Capri 606 TV (17") restoration

Even with the old selenium in place, the voltage across the capacitors would go to around 320-325V at power on. The selenium does have a lot more internal resistance than a silicon diode, but with no load being drawn from the rest of the TV during the power on, the voltage would be not a lot lower than with a selenium rect. If selenium works fine, I would keep it if it was my TV. I never seen them fail in a violent way. Either they worked fine with proper voltages (albeit a few % lower than on the schematics), or were worn out with outputting lot lower voltages.

I think the capacitors would not care too much with a 325V applied since they were much more tolerant on the voltage back in a day. But still it is a bit odd to have only 320V rated capacitors since the electrolytic capacitors in TVs with direct mains AC rectification were usually 350V/385V rated.

Just from my notes, about the NTCs in heater circuit. I worked on a 1958 Philips TV that did implement a heater NTC series resistor, but interestingly a bit newer, but similar 1960 Philips TV omitted it, presumably that they used all valves with controlled heat up time or they found out that the heater failure on the valves is not too common. On the later 1960s TVs I never came across another NTC in the heater. Also I don't recall when it was last time I got a P series valve with an open heater. So I think you are also okay without one
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Old 10th Jan 2021, 10:21 am   #89
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Default Re: B&O Capri 606 TV (17") restoration

I wish I could remember the Capri, I was in the trade then (just)
Sets using that EHT rectifier were the norm. Until recently I had a B&0 2000 (i think I'm right on model)
This was a hybrid colour, perfect picture, but well done on your Capri!
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Old 21st Jan 2021, 10:47 pm   #90
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Default Re: B&O Capri 606 TV (17") restoration

Hi Mitch,
You got me thinking. The selenium rectifier causes the DC voltage to be low by about 30Vdc. It still works, but it is not really satisfying to know it is so much out of spec. Since the PSU section is so minimal, I decided on implementing a transformer in bucking mode - a small toroid, which I mount on a custom made bracket. I agree on keeping things original, so all things I make can be reverted. No extra holes are drilled in the chassis, etc.

With the transformer in place and the 1N4007, the voltage I measure at the capacitors peak out at 285Vdc.

Currently, I'm awaiting some ~100 ohm PEV-25 and some 7.5 ohm PEV-10 resistors to arrive from Romania. Those are for the filament section. But when everything is in place, I'll post some pictures of the change.

I have attached a few Capri PSU schematics. The predecessor 514K (model year 59) uses the VA1015. The 606 and 607 (model years 60 and 61) do not use the VA1015. The Capri 610 (model year 64) uses the VA1015 once again. I think I'd prefer to have the VA1015, as even the CRT heater glows up quite a bit more than it should for some seconds without it.

Tony,
Thanks - the Capri 611 schematic is the first multilingual schematic I can find, so 1965 may be the first year B&O started exporting TV's, and the 611 seems to be the last year for the Capri range, before "Beovision" was born a year later. So this could explain why you don't remember the Capri series.
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Old 22nd Jan 2021, 12:17 am   #91
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Default Re: B&O Capri 606 TV (17") restoration

Please note that if you want to adapt the filament circuit for a higher mains voltage, you should measure the current to be as close to 300mA as possible to the nominal mains voltage (230V I presume) with a few percent under, being slightly better than a few percent above. Not more than 5% though, as per Philips valve specifications for series heated valves (for parallel heated valves, measure the voltage instead of the current). The set will likely perform fine within 10-20% mains fluctuation, but as close to the nominal current as possible will give the best valve and tube life.
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Old 23rd Jan 2021, 11:03 pm   #92
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Default Re: B&O Capri 606 TV (17") restoration

Thanks Maarten. With exactly 230Vac from the variac, and with 105 ohms and the VA1015 heated up for a long time, the current draw is 305 mA. I'll see what I can do with the 100 ohm resistor and the 7.5 ohms once they arrive.

The current drawn from the bucking transformer is "unfortunately" 645 mA. The toroidal secondaries, which I presume is what sets the limitation of the current draw, are rated for 750 mA, and they specify on the transformer to use a 650 mA fuse. Hopefully it is ok. It doesn't get warm.
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Old 26th Jan 2021, 12:42 am   #93
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Default Re: B&O Capri 606 TV (17") restoration

I'd say 305mA is pretty good, only +1,7% from nominal but since you already ordered some resistors you can always see if you can get it closer to 0%.
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Old 9th Feb 2021, 9:56 pm   #94
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Default Re: B&O Capri 606 TV (17") restoration

Change of plans; a variable 120 ohm 25W was fitted. With 108 ohms, the current is 297 mA with a nominal 230Vac line voltage. Now I'm Happy, Maarten

So for anyone else working on a Capri 606/607 in the future (who knows...): The 120 Ohm Vitrohm type DJ filament resistor was replaced with a VA1015 NTC and a 108 ohms resistor.
The smaller resistor connecting the 120 ohm and 15 ohm is removed, and after the filter choke, a 15VA toroidal transformer is placed to drop the voltage about 20V (bucking mode). The output goes to a 1N4007 followed by an 18 ohm resistor to compensate for the increased efficiency of the 1N4007. I used Ohmite 12SE-10 mounting brackets for the resistors, but modified them to bring the resistors closer to the chassis. Otherwise, the clearance to the CRT would only be about 1.5 cm.

I tested with the "new" AW43-88 too. I'll need to adjust the centering again soon.
One thing I found strange with this CRT is that the center region appears more green than the rest. Seems to improve a bit with use. I don't see any discoloration of the phosphor. Hopefully it is fine. It is a little visible in the attached image.

I'm also trying to figure out why on both CRTs, the image brightness changes briefly - a flickering once in a while, but not with any certain periodicity. I guess this must be related to G1, but not sure where it is likely caused. I'm tending more towards the brightness pot itself, with the 50n (47n) cap to ground as that has a time constant that would be long enough to be visible. Maybe someone has a better suggestion
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Old 21st Feb 2021, 12:21 am   #95
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Default Re: B&O Capri 606 TV (17") restoration

Quick update:
I managed to fix the flickering, and actually thanks to you Hugo (PortugalTV) and your suggestion of temporarily removing capacitor 69. When I pause the video, there is no problem, as long as the image doesn't contain a lot of contrast. So it struck me that this could be the video feedback to the contrast pot through component 69, the 5uF capacitor in the schematic that forms a high pass filter together with the pot and other resistors.
The PCB that is used for the video section is that of a Capri 607, which for some reason means that some component values have changed. Instead of the 5uF, a 22uF cap was used, and I just went for the same value when replacing the cap. The increased capacitance caused the time constant to be much too long.
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Old 21st Sep 2021, 9:38 pm   #96
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Default Re: B&O Capri 606 TV (17") restoration

Thread reopened at OP's request.
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Old 22nd Sep 2021, 9:19 am   #97
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Default Re: B&O Capri 606 TV (17") restoration

Thank you, Graham.

The project has been at a near stand-still for some time. In the mean time, replica teak legs have been turned.

But for now, I'm still really annoyed by one thing that I can't seem to find the real cause of: Random brightness flashes. I have included a video to show what it looks like: https://vimeo.com/610903414 - it is around 0:05 to 0:07 and then again at 0:40 to 0:47 .
I suspected that it was visible on G1 of the CRT - but using a oscilloscope, I can't seem to detect any abnormalities. As the abnormalities are so short, they are hard to decipher from the rest (blanking pulses).
I suspected a dirty brightness pot, so I tried substituing with resistors for the time being, but no change.
The brightness flashes only seem to occur after the set has been on for at least 10 minutes. Sometimes less. That's why I don't think it is an AGC problem, like I previously thought.

So, I'm reaching out to someone more knowledgeable on this - maybe this was a commonly seen problem back in the days, with a known cause? Or does anyone have a guess?

I have checked each and every solder joint, and cleaned and inspected all tube sockets to no avail.
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Old 22nd Sep 2021, 4:02 pm   #98
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Default Re: B&O Capri 606 TV (17") restoration

Hi,
This flickering could come from:
- valve sockets
- inner connectors
- bad solder connections
- dirty tuner contacts
- bad valves
- bad controls

The best way to find that source of issues is carefully knocking on all parts,
moving the wiring, by watching the screen.
Carefully - with something isolated or something like a longer plastic rod.

Good luck!
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Old 25th Sep 2021, 3:42 pm   #99
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Default Re: B&O Capri 606 TV (17") restoration

Thank you German Dalek. Your mention of dirty tuner contacts got me to think about one thing that I found regarding the turret tuner: It is slightly more offset from the contact points in one end, compared to the other. Actually it was so much that it barely made contact in one end.
I have filed down one end of the joint support by about 0.5 mm, and the result can be seen from the attached image. Result is not perfect, but better than before, and the filing does not seem to have de-tuned the tuner.

Now, the next problem has started: EHT is down to 12.8 kV - brightness can still be increased to max without picture disappearing. Not sure if I should be concerned yet - or what I should do. Windings slowly shorting out? I thought that the EHT would always fail with a "bang".
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Old 27th Sep 2021, 6:28 am   #100
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Default Re: B&O Capri 606 TV (17") restoration

Hi,
I should control the parts and tubes of the horizontal line stage.
- all resistors
- all caps
- all tubes (swap them with tubes from a working set)
- test the voltages (VTM & scope)

A line short of the LOPT leads to a flickering in the lines,
that means a few lines break out and are going to dance left and right.
This could be a little bit noisy.

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